Luvailin appears only in the Unfinished index. The name Shadowmere is said to be its "translation".[1] Though Tolkien did not provide an explanation of the latter, fans have speculated that Luvailin seems to contain the elements luv- *"shadow-" (seemingly from √LUM, LUB "shadow, darkness",[4]) and ailin "pool, lake"[5],[note 1] and that it is unclear if the name is supposed to be Quenya or Sindarin.[6]